This invention relates to a positioning joint for a folding ladder.
In a conventional positioning joint for a folding ladder, the folding or unfolding of the ladder to a desired angular position is performed by aligning holes in side discs and inserting a pin through the aligned holes. A joint of this type has the disadvantage that it is difficult to quickly align the holes simultaneously.
Another prior art joint for a folding ladder utilizes a ratchet. However, users must be concerned about the safety of such a joint because of potential malfunctions of the ratchet.
A further positioning joint for a folding ladder utilizes a U-shaped member as a control means, as set forth in U.S. patent application Ser. No. 073,585. Two joint members are relatively pivotable about a common axis, the joint members being lockable in a series of predetermined angular positions by engaging a spring-biased pawl, provided within one member, in notches formed at the peripheral edge of the other member. A control means in cooperation with a manually operated lever controls the locking and unlocking of the joint.
Although this type positioning joint insures safety in use while being easy to operate, it has a drawback in that its construction is somewhat complex and costly to manufacture, and has a further disadvantage in that it is cumbersome to operate the lever.